Manufacture of incandescent filaments.



UNITED STATES PATENT OFFICE. casran-nonxsvmn, or rims, 'rnhn'cn', Assmnon 'ro 'sccinrn rnrnnnnrfitonimn DE LA LAMPE nnnormouno. a, or teams, rmc'n, nconteonnrron'or muss.

manna-servants r cannmsm murmurs.

No Drawing.

' Speci'flcationot mars Patent. Appticat'ion flliediuly b 1999. Serial No.'506,869.

To all whom it may concern 'Be it known that I, GAii'rA'N Donx'nvrrcrn; of 81 Rue de 1Assomption,-Paris, France; engineer, have invented a new and useful Improvement'in the Manufacture of Incandescent Filaments, which improvement is. fully set forth "the following specification.

In the manufacture of incandescent lamp filaments by drawing a paste, composed of' metals or of their compounds with or without addition of lampblack agglomerated by a binding agent, the carbon is first 'elimi-' nated from the filament which is then brought to or maintained in a coherent metallic state. The two operationsof decarburization and metallization may be performed successively or simultaneously =according to the nature of the gaseous mixture which servesfor the formation. :Fhe term 'metallization can be equally well employed whether applied 'to meta-ls prop erly so called or to metalloid conductors of. electricity other than carbon 'fcr' designat. ing the operation by which they are brought to the state of simple elements. In allknown processes the carbon is eliminated by oxidation, which "may however =be'-in the presence of an excess of hydrogem'which rings the filament to or maintains it in a metallic state. A process has been described in an application of like date in which sulfur is employed for this purpose. in all these processes metall-ization is brought about by the reducing action of hydrogen in excess upon the metallic oxid or sulfid. It is evident that these methods are only applicable to such metals or metalloids 'as are "not attacked by oxygen or sulfur to form oxids or sulfids which cannot be reduced in hydrogen at temperatures lower than their volatilization point. This is the'case for the majority of the metals useful in lamp-filaments and especially those of the osmium and tungsten groups. But the oxide -of metals such as those of the group of which vanadium, niobium and titanium form part do not appear to be completely reduced by hydrogen "even at very elevated temperatures. Their higher oxids' are merely brought to a lower state of oxidation but not to the state of simple elements.

The process which forms the "subject of the present invention allows incandescent filaments to be obtained in apracti'cal manner even when oxids are employed which cannot be directly reduced by hydrogen without destruction of the "filaments.

Under the @present invention filaments are obtained by drawing in the usual manner a paste composed of metals of the described class or of their chemical combinations. Preferably the paste is composed of the lower -o2r'ids,the higher oxids and lampblack being added :if'desired. The metalliferous "filaments arethen heated in the air at a temperature below 'a red 'heat, "or, and preferably, to a red heat out of contact with the air; or in --a reducing atmosphere com- P sed of hydrogen or a gaseous mixture of hydrogen and'oxidizing gases or vapors containing hydrogen-in excess with respect to the oxidizing gases; The filament thus be- =comes -aconductor ofelectricity. It is now subjected -to a decarburiz-ing operation which consists in bringing it to a red 'heat' in an atmosphere formed ofa gaseous mixture which oxidizes or sulfurizest-he carbon but which is of 'aredu'cin nature in order that the filament tmay sti l donduct electricity.

hen the filament has been decarburi-zed, it is according-to thepresent invention then metallized bringingit to a higher temvperature than-before in an atmosphere con- 'tai-ning a mixture of -hy-(h'o'gen and amunonia admixed with small quantities of oxidizing and sulfurizing gases if desired. "When the filament is brought to a white heat metallization proceeds rapidly. However if the temperatureof the filament be brought above the given limit, the filament maybe destroyed.

Thereaction produced may be interpreted as follows: The ammonia dissociates by heat and furnishes nitrogen and hydrogen in the nascent state, which consequently possess greater chemical activity than usual. The oxid 'of the filament-forming elementis decomposed, steam and a nitrid of the element constituting the filament being produced. The nitrid however is immediately decom- PatentedO'ct. '28, 1913.

posed by the excess of hydrogen and the filav ment immediately metallized. Nitride of the filament-forming element may 'also be employed in the composition of the paste from which the filament is drawn; and when they are electric conductors and capable of reduction by hydrogen the filament may be dccarburized and metallized in an atmosphere containing hydrogen in large excess.

In order to prevent the destruction of a filament by too high a temperature, this term perature should correspond to that of volaquently serve for decarburization; but as these gases are very poisonous it is preferable to avoid such formation.

Simultaneous decarburization and metallization may be obtained by operating in suitable gaseous mixtures. The amount of nitrogen in the mixed gases should not exceed a certain proportion or it will be impossible to metallize the filament since this gas unites directly at a high temperature with vanadium, titanium and their analogues. The formation of the filaments takes place in chambers or furnaces filled or traversed by the gaseous current and the portions of the useful gases not taking part in the reactions of formation may be recovered.

The ammonia used in the process may be introduced into themixture in the state of ammonia prepared beforehand, or it may be generated in the vessel by the action of electric sparks or arcs upon a mixture of hydrogen and nitrogen, or by the decomposition in a chamber filled with hydrogen, of a compound capable of furnishing nitrogen by virtue of a suitable reaction, as, for example the decomposition of the oxygen or halogen or other salts of ammonia by heat or electricity.

The filament thus metallized (upon the same support which has served for the for mation or upon a different support) is introduced into the bulb in which a vacuum is formed. The filament is fixed to hooks, of very refractory metal, on the support by means of a cement which does or does not leave, after formation, a metallic residue of the same nature as the filament (this residue may be difierent provided that it resists very high temperatures). Vhen the cement does not leave a residue the filament solders to the hooks which conduct the current by the fusing together of the metals at the point of contact.

When the filament is mounted in the lamp upon a support different from that which has served for the formation it may be fixed to the leads either by means of a suitable cement or by autogenous soldering or by soldering with a difierent material from that which forms the hook and the filament. But as filaments of vanadium, titanium, niobium and similar bodies are attacked'by nitrogen the soldering cannot be carried out in a current of this gas as can be done with a -filament of tungsten, osmium and similar bodies. An atmosphere of hydrogen must be used for this purpose. But when soldering by means of an electric current, as hydrogen ignites easily the gaseous current must be suflicient in quantity to insulate the point to be soldered from the surrounding air for a suflicient distance.

It is preferable to heat the solder by the action of a sufiiciently strong current and to employ the more fusible solders such as copper or silver. Aluminum or zinc may also be used as solders.

There are particular difliculties in obtaining a suitable vacuum in lamps having vanadium, titanium or like filaments when the present process of formation of the filament is employed because these bodies unite directly with nitrogen. In order that the filaments may be durable it is necessary that the bulbs should have a given vacuum but not an absolute vacuum and there must be some residual gas. If the vacuum be pushed too far, the filament perish'es too quicklyand the lamp blackens.

For lamps having vanadium, titanium and' similar filaments, the process of lamp making is as follows: The bulb is thoroughly exhausted and the filaments are brought to incandescence in order to release the occluded gases: Then preferably air from which the oxygen may have been removed is-again allowed to pass into the bulb, which is again exhausted to a determined pressure. This pressure is calculated in such a manner that the volume of gas remaining contains sufficient inert atmospheric gas such as argon, helium and the like to give a pressure corresponding to the normal vacuum of incandescent lamps after the nitrogen and oxygen have been extracted. The exhaustion of the nitrogen takes place by bringing the filaments to incandcscence either by utilizing for this purpose special filaments of the same metal or of a different nitrogen absorbing metal (in this case it will be necessary to bring the filament to incandescence before closing the bulb in order that the atmosphere in the different bulbs may be homogeneous) or by utilizing for this purpose metals such as calcium or magnesium which when heated to a suitable temperature absorb by occlusion or chemical combination nitrogen and nearly all the other. gases except hydrogen and the so-called inert gases. If pains be taken to prepare in a separate vessel a certain quantity of these inert gases (argon, helium, neon, etc.) by absorption of the nitrogen and the oxygen they may be introduced into the bulb after.

having exhausted it as completely as pose 3. In the manufacture of It is evident that the present process which is in reality of the metals such as vanadium, titanium, niobium, etc., in a state of purity can be applied to these bodies in a general manner whatever the use to which they are to be ut. p Having now particularly described and ascertained the natiire of my said invention and in what manner the same is to be performed I declare that what I claim is:

1. In the manufacture of incandescent filaments, the process which comprises heating a metalliferous decarburized filament in an atmosphere comprising hydrogen and ammonia.

2. In the manufacture of incandescent filaments, the process which comprises heating a filament comprising an oxid of a metal of the vanadium class in an atmosphere comprising hydrogen and ammonia.

incandescent filaments, the process which comprises heating a filament comprising an 'oxid of a metal of the vanadium class in an atmosphere comprising hydrogen and ammonia and then surrounding said filament with an atmosphere of inert gases.

4. In the manufacture of incandescent filaments, the process which comprises preparing a filament comprising an oxid of a metal of the vanadium class, ment and heating in an atmosphere comprising hydrogen and ammonia.

5. In the manufacture of incandescent filaments, the process which comprises preparing a filament comprising an oxid of a metal of the vanadium class, metallizing said filament, heating in an atmosphere comprising hydrogen and ammonia and then surrounding with an atmosphere of inert gases.

a process of preparation metallizing said fila- 6. In the manufacture of incandescent fila;

process which comprises heating to a white heat a metalliferous decarbonized filament in an atmosphere comprising hydrogen and ammonia.

7. In the manufacture of incandescent filaments, the process which comprises heating to a white heat a filament comprising an oxid of a metal of the vanadium class in an atmosphere comprising hydrogen and amments, the

' monia.

8. In the manufacture of incandescent filaments, the process which comprises heating to a white heat a filament comprising an oxichof a metal ofjthe vanadium class in an atmosphere comprising hydrogen and am-. monia and then surrounding said filament with an atmosphere of inert gases.

9. In the manufacture of incandescent filaments, the process which comprises preparing a filament comprising an oxid of a metal of the vanadium class, metallizing said filament and heating the same to a white heat in an atmosphere comprising hydrogen and ammonia.

10. In the manufacture of incandescent filaments, the process which comprises preparing a filament comprising an oXid of a metal of the vanadium class, metallizing said filament, heating the same to a white heat in an atmosphere comprising hydrogen and ammonia and then surrounding with an atmosphere of inert gases.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses. v

GAETAN DOBKEVITCH. Witnesses H. O. Coxa, Fmior'zmc HARLii. 

